• Journal of Life Science
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• v.30 no.9
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• pp.819-825
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• 2020

All living organisms exhibit the characteristics of aging, such as skin wrinkle formation, muscle degeneration, cataracts, and hair graying as the number of aged cells increases over time. Senescence, which is known as a key cause of aging, is directly related to the aging of living organisms because cells are aged by external and internal factors and eventually cell proliferation is stopped. Senescence is caused by the gradual shortening of the telomere with cell division, and lifespan is determined by the length of the telomere. Recently, it has been found that the histone deacetylase, which can influence gene expression, is not only involved in yeast but also deeply involved in anti-aging mechanisms in both C. elegans and humans. It was also discovered that old cells play a decisive role in the aging phenomenon, and it has been reported that it is possible to promote the proliferation of young cells and delay aging by removing these senescent cells from the inside. Therefore, in order to develop potential anti-aging agents in the future, research should begin with an in-depth study of telomerase activators, sirtuin activators, and senolytics.

• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.1114-1123
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• 2015

Bushing is the key link to connect outer and inner insulating systems and also the essential electric accessory in electric power system, especially in the high voltage engineering (AC 1000kV, DC 800kV). This paper presented the experimental research of thermal aging characteristic of oil-paper insulation used in bushing. A thermally accelerated aging experiment at 90℃ was performed. The bushing models containing five layers of paper were sealed into the aging vessels and further aged for 250 days. Then several important parameters associated with the aging were observed and evaluated. The results showed that the degree of polymerization (DP) of papers gradually decreased. The DP values of outermost layer and middle layer fit well into the second-order kinematic model and first-order kinematic model, respectively. Less deterioration speed of the inter-layer paper than outer layer was confirmed by the variation of DP. Hydrolysis was considered as the main cause to this phenomenon. In addition, the logarithm of the furfural concentrations in insulation oil was found to have good linear relationship with DP of papers. Interestingly, when the aging time is about 250 days and DP is 419, the aging process reaches an inflection point at which the DP approaches the leveling off degree of polymerization (LODP) value. Both tanδ and acid number of oils increased, while surface and volume resistivity of papers decreased. The obtained results demonstrated that thermal aging and moisture absorbed in papers brought great influence to the degradation of insulating paper, leading to rapid decrease of DP and increase of the tanδ. Thus, the bushing should be avoided from damp and real-time monitoring to the variation of tanδ and DP values of paper is an effective way to evaluate the insulation status of bushing.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.3
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• pp.855-864
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• 2013

The dynamic characteristics of natural rubber bearings, which are used as isolator, are dependent on the main rubber's dynamic behaviors and nonlinear properties. Rubber materials tend to undergo an aging process under the influence of mechanical or environmental factors, so they inevitably end up facing damage. A main cause of aging like this is known to be oxidization, which occurs through the heat of reaction at high temperatures. Accordingly, in this study an accelerated thermal aging test was carried out in order to compare the characteristic values of the bearings before and after thermal aging occurs. As a result of this experiment, it was found that a thermal aging phenomenon could have some effects on shear stiffness, energy absorption, and equivalent damping coefficients of the bearings. Furthermore, a deterioration in the dynamic properties of the natural rubber bearings caused by the thermal aging was applied to an actual bridge and then the effects of such thermal aging on the seismic performance of the bridge were also compared and analyzed based on numerical analysis. As a result of this analysis, it was found that the changes in the basic properties of the natural rubber bearings caused by the thermal aging bring only a minor effect on the seismic performance of bridges.

• Journal of Physiology & Pathology in Korean Medicine
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• v.24 no.4
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• pp.533-542
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• 2010

Skin aging is a natural phenomenon. There are internal and external factors of skin aging. The internal factor of skin aging is from the wearing down of the body over time. The external factors are more noticeable from habits such as smoking, excessive alcohol, malnutrition, and extended exposure to UV rays. Completely stopping skin from aging is impossible but one can slow down and treat external signs of skin aging. In western medicine, the following methods are used to reduce the appearance of skin aging: applying lotions and creams containing ingredients such as fruit acid, antioxidants, plant exracts, depigmentation, moisturizer, retinoids, and sun block; botulinum toxin injections; chemical peels, laser and other painful methods remove the top layer of skin to promote new skin growth; fillers are injected to increase soft tissue growth; surgery. In oriental medicine, the following methods are used: acupuncture into facial muscles which stimulates acupuncture point; applying topical treatments and cosmetics containing herbs are effective of preventing skin aging and wrinkles. Above all thing, medicine that helps maintain essence and blood in the skin can be fundamental.

• Toxicological Research
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• v.19 no.3
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• pp.161-172
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• 2003

Explanted mammalian cells perform a limited number of cell division in vitro and than are arrested in a state known as replicative senescence. Such cells are irreversibly blocked, mostly in the G1 phase of cell cycle, and are no longer sensitive to growth factor stimulation. Thus replicative senescence is defined as a permanent and irreversible loss of replicative potential of cells. For this characteristic, replicative senescence seems to evolve to protect mammalian organism from cancer. However, senescence also contributes to aging. It seems to decrease with age of the cell donor and, as a form of cell senescence, is thought to underlie the aging process. Extensive evidence supports the idea that progressive telomere loss contributes to the phenomenon of cell senescence. Telomeres are repetitive structures of the sequence (TTAGGG)n at the ends of linear chromosomes. It has been shown that the average length of telomere repeats in human somatic cells decreases by 30∼200 bp with each cell division. It is generally believed that when telomeres reach a critical length, a signal is activated to initiate the senescent program. This has given rise to the hypothesis that telomeres act as mitotic clocks to regulate lifespan. One proposes that cumulative oxidative stress, mainly reactive oxygen species generated from mitochondria, may mainly cause telomere shortening, accelerating aging. Here, the biological importance and mechanism of replicative senescence were briefly reviewed. Also it was summarized that how oxidative stress affects replicative senescence and telomere shortening.

• Korean Journal of Human Ecology
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• v.8 no.4
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• pp.57-69
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• 2005

An aging society in which the proportion of the aged of a society is growing faster than the of the young is becoming an worldwide phenomenon owing to low birth rate, the upgraded medical art and so on. Korea is one of the most rapidly aging societies in the world today. Since aging society is totally different from the traditional society in the many field, potential problems must be expected and countermeasure must be considered. One of the potential problems it may cause is the issue of supporting subject of the aged. Parent-supporting and welfare for the aged become important social issues. Especially the supporting of the aged woman is more important issue because of their longer average life than man and their exposure to sexual discrimination and their welfare is very important issue of social welfare system. Accordingly the purpose of this study is to present the practical counter measure to the supporting of the aged woman. These studies can be divided into traditional approach which insists on the family supporting and modern approach which asserts government(or social) supporting. Comprehensive literature study reveals that both of government and family are responsible for the supporting of the aged woman.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.2A
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• pp.109-116
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• 2012

The dynamic properties of lead rubber bearings, which are used as isolator, are dependent on the main rubber's dynamic behaviors and nonlinear qualities. Rubber materials tend to undergo an aging process under the influence of mechanical or environmental factors, so they can end up inevitably facing damage. A main cause of such aging is known to be oxidization, which occurs through the heat of reaction at high temperatures. Accordingly, in this study an accelerated thermal aging test was carried out in order to compare the characteristic values of the bearings with each other before and after thermal aging occurs. As a result of this experiment, it was found that a thermal aging phenomenon could have an effect on shear stiffness, energy absorption, and equivalent damping coefficients. Furthermore, a decline in the dynamic properties of the lead rubber bearings by means of the thermal aging process was applied to an actual bridge and the effects of such thermal aging on the seismic performance of the bridge were also compared and analyzed based on numerical analysis. As a result of this analysis, it was found that the changes in the basic properties of the lead rubber bearings have a minor effect on the seismic performance of bridges.

• Journal of Applied Reliability
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• v.7 no.4
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• pp.163-172
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• 2007

Phenomenon, such as hardening, cracking or breaking etc.. of PVC tape for wiring harness by aging were detected on driven automobile in field. Hardening or cracking of PVC tape were confirmed decline of elongation by surrounding stress. The accelerated heat aging test was carried out applying temperature most important factor of aging, and then deduced an equation of useful life using arrhenius model. Prediction method of useful life of PVC tape was developed using miner rule calculating damage value by thermal energy classified temperature by matching deduced equation of useful life and measured temperature value on driven automobile in field.

• Health Policy and Management
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• v.27 no.4
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• pp.372-374
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• 2017

Korea is one of the fastest aging country in the world. The increase in health expenditure is an inevitable problem in an aging country. We examined trend of benefit expenditure in National Health Insurance (NHI) by age group during 2001 to 2016. The benefit expenditure of NHI was 13.0 trillion won (2001) and 48.7 trillion won (2016); that is 3.76 times to 2001. This rapid increase was mostly due to people aged 65 and over. Proportion of beneficiaries aged 65 and over was 6.9% (2001) and 13.7% (2016), benefit expenditure per capita aged 65 and over was 279 thousand won (2001) and 960 thousand won (2016), and utilization days per capita aged 65 and over 21.44 (2001) and 30.23 (2016). This phenomenon was more pronounced in 75 or 85 aged and over. To contain the health costs for older people, the NHI system should be reformed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1993.05a
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• pp.88-91
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• 1993

In this study 9.5/65/35 PLZT was selected which has the excellent quadratic electro-optic property and slim-loop. It was fabricated by the methods of vacuum hot-pressing and sintering. The electrode of color filter was evaporated using the interdigital type masks. Hysteresis and transmission characteristics were measured. The coercive field and the nontransmited field were correlative. Aging effect was measured according to time at same temperature. Wavelengths of RGB were chosen 700[nm] for red, 545[nm] for green and 435[nm] for blue by the standard of the Commission Internationale del Eclaiage.